Apparatus for recording electric alternating currents by means of a voltaic arc



June 21, 1932. KQNEMANN 1,863,560

APPARATUS FOR RECORDIN LECTRIC ALTERNATING CURRENTS BY MEANS A VOLTAIG ARC Filed Oct. 20, 1928 Patented June 21, 1932 UNITED STATE HEINRICH KGNEMANN, OF MUNSTER, GERMANY APPARATUS FOR RECORDING ELECTRIC ALTERNATING CURRENTS BY MEANS OF A VOLTAIC ARC Application filed October 20, 1928, Serial No. 314,307, and in Germany October 29, 1927.

The devices for improved recording of electric alternating currents by means of a voltaic are such as set forth in my copending application, Serial No. 277,678, filed May 14, 1928, are further developed according to the present invention for the purpose of obtaining more exact recording.

The present invention consists in arranging in the said device, a means which produces a proportionality between the form of the alternating current and the emitted light of the are.

In order that an electric current shall pass through a gas, a definite amount of ionization of the gas particles between the electrodes is necessary; and this amount of ion ization is proportional to the current intensity. If, therefore, the amplified alternating current of a microphone, for example, is superimposed upon the direct current of the arc, then the degree of ionization of the gas particles between the electrodes must fluctuate in periodicity with the superimposed alternating current. Since the light which serves for the photographic recordation of the sound is dependent upon the degree of ionization, it is a requirement for proper recording that the ionization of the arc shall increase and decrease in exact correspondence with the superimposed altelrnating current from the microphone.

However, if the electrodes are very hot, then their high temperature will cause gas particles near them to remain ionized although the current has decreased, or in other words the emitted light from the arc is no longer at this time proportional to the superimposed alternating current.

A simple method for the purpose of maintaining the desired proportionality consists in keeping the temperature of the electrodes low. The ionization of the gases in the path of current can then follow the fluctuations of the current passing through in a better mannor, whereas at ahigher temperature of the electrodes, the latter keep the gas particles in their proximity ionized for a longer time.

The consequence of this is that the electrical fluctuations which correspond to the sounds are more easily transformed into luminous fluctuations; in other'word s, with oxidized electrodes the photogram of the sounds is much better formed and much richer in lines than that made without metal oxides.

To keep the temperature low, metal oxides may be employed for the electrodes. The electrodes themselves may be oxidized or they may be covered with an oxide. The oxide coated electrodes give olf the electrons more easily than the simple metal. A voltaic arc employing oxide coated electrodes does not require so great a current intensity as a lamp employing simple metallic electrodes, and hence the oxidized electrodes do not require so high a temperature. T heioniza'tion in the gas therefore corresponds to the current intensity being transmitted across the gap, and substantially no auxiliary or heat ionization occurs. Therefore, with the change of the current intensity, the ionization changes in a like ratio and in the same direction, without any damping or deadening of the immediate response by the effect of the heat-ionized gas particles, so that the ionization at any instant exactly-corresponds to the current intensity of the direct current as modulated by the alternating current. It is easily seen from thestrength of the light in such a case, (all other conditions being the same) that the temperature of the oxide electrodes is lower than in an are between eletcrodes of pure metal.

On the accompanying drawing is re resented a recording apparatus for sound fi ms according to this invention, in one form of execution; which drawing shows:

Figure 1, a circuit diagram.

Fig. 2, a detail of the recording lamp in vertical section.

Fig. 3, a detail of the ends of the electrodes, provided with. an oxide coating, in longitudinal section on a larger scale than in Fig.2.

The tungsten arc lamp L (Fig.1) is supplied from the direct current mains through an intercalated resistance VV and a choke coil D. The currents from the microphone. M- are then superimposed upon the direct ourrent by means of the transformer T. The

resistance serves as a steadying resistance for this alternating current. The condenser 0 opens a path for the alternating current while it closes this path to the direct current. The choke D keeps the alternating current away from the direct current mains. The luminous fluctuations in the lamp L are fixed by this apparatus upon the passing film F.

The tungsten arc lamp L is represented in detail in Fig. 2. The electrodes 1 and 2 have a voltaic are 7 burning between them; these electrodes being held in the holders 3 and 4 supported in the glass foot 5, within the glass vessel 6 which shuts oii the interior of the lamp with respect to the atmosphere. The electrodes 1 and 2 are covered with oxide as may be distinctly seen in Fig. 8.

In operation, the intensity of the volatic are 7 in the lamp L fluctuates in accordance with the superimposed or modulating alternating currents from the microphone M in their efiect upon the direct current supplied to this arc lamp. By employing the metal oxides to coat the electrodes 1 and 2, the temperature of maintaining the arc is maintained below the point of substantial ionization of the gas employed within the enclosing vessel 6.

Claims:

1. The method of recording sound by means of a voltaic are operating between oxide coated electrodes in a gas, which comprises passing a direct current therethrough to produce the ,voltaic are at a temperature below the point of substantial heat ionization of the gas, and modulating the direct current by a sound current whereby to vary the light intensity of the arc, and recording the light fluctuations of the are.

2. An apparatus for recording sound, comprising a voltaic arc lamp including tungsten electrodes having a coating of metallic oxide and a gas containing envelop surrounding said electrodes, a source of direct current to operate said lamp at a temperature below that of substantial heat ionization of the gas. and means to modulate the light intensity of the grc according to the sound intensity and including a microphone and circuits for connecting the same to the said electrodes.

3. An apparatus for recording sound by means of a voltaic are modulated in intensity by an alternating electric current and having tungsten el e ctrodes, including a coating of metal oxide on the tungsten electrodes to make the light emission of the recording are more conformable to the alternating current superimposed to the direct current of the arc, and a source of current to heat said coatings to a temperature below that of substantial heat ionization.

Intestimony whereof I have signed my name to this specification.

' HEINRICH KONEMANN. 

